In a fuel-injected internal combustion engine, an electronic control unit (ECU) turns on the fuel injectors at the appropriate time to inject fuel into the cylinders. The percentage of time a fuel injector is open during the fuel cycle is known as the fuel injector duty cycle. Input data to the vehicle ECU, i.e., engine RPM, throttle position, crankshaft position and the like, are provided by factory installed engine sensors. The vehicle manufacturer provides stock ECU programming defining the fuel injector duty cycle for each value of throttle position and engine speed, which determines the fuel economy, power and emission levels for the vehicle.
Aftermarket fuel management systems that modify the performance of fuel-injected engines in cars and motorcycles are known. The Power Commander® fuel injection control module available from Dynojet Research Inc., North Las Vegas, Nev. 89081 is one such fuel management system.
The fuel management system is composed of a fuel management module and its associated software that enable the user to modify vehicle performance. A fuel management module is installed in-line between the vehicle ECU and the fuel injectors. The fuel management module affects engine performance by modifying the duty cycle of the fuel injectors by adding or subtracting from the fuel injector duty cycle. Specifically, the fuel management module contains a fuel map that defines how much the fuel injector duty cycle is to be increased or decreased for each value of throttle position and engine RPM. In particular, for each value of throttle position (expressed as a percentage of full throttle) and engine speed (in revolutions per minute, or RPM), the cells in the fuel map provide a corresponding fuel adjustment or “offset” to the stock programming provided by the vehicle manufacturer.
The manufacturer of the fuel management system typically provides one or more fuel maps that optimize a given performance criteria. For example, the user can choose one fuel map to optimize fuel economy or another fuel map to optimize towing capacity. Alternatively, the user can choose a fuel map that optimizes performance by maximizing acceleration or top speed. The user can also modify individual values of a fuel map to tune the vehicle. In such manner, the user is able to tune the performance of the vehicle.